1. Field of the Invention
This invention relates to a method and an apparatus for fermentation of cattle dung, sewage sludge, pulverized kitchen garbage or like sludgy or nearly sludgy organic waste material mainly containing high percentage of water.
2. Description of the Prior Art
Conventionally, a method for fermenting the above organic waste material for effective applications to a solid organic fertilizer and a soil amendment material or the like has been widely known, as disclosed in Japanese Patent Publication No. 59-18353, for instance.
For fermentation of the organic waste material, a treating object material is dehydrated or mixed with dried straws, husks or like vegetable fiber materials containing low percentage of water for control of the water content of the treating object material until a predetermined or less ercentage of water content (in the range of 60 to 65% generally) enough to permit aerobic fermentation is reached. Then, the material subjected to control of the water content is fed into a fermentor for aerobic fermentation through the supply of warm air or the like till the initial starting stage of fermentation.
However, the limit of the percentage of water content controlled according to the method and the apparatus in the prior art is 65% at most, while the ideal percentage of water content is considered to be not more than 60%. For that reason, disadvantages in the prior art are that the treating object material needs to be hydrated or to be mixed with a large quantity of water-content control material, and much time is required for such hydrating or mixing works and fermentation decomposition.
Since an apparatus for aerobic fermentation (primary fermentation) in the prior art only permits primary fermentation, it is necessary for anaerobic fermentation (secondary fermentation) following the primary fermentation to install an apparatus for secondary fermentation of a primarily fermented material taken out from the fermentor used for primary fermentation. There is also a need for a material cutting work in the course of secondary fermentation and also a fermentation facility having a floor of a size enough to perform the cutting work. Thus, the apparatus for fermentation in the prior art is not economical from the points of installation cost and management of fermentation.
The present invention is to provide a method and an apparatus for fermentation of an organic waste material for eliminating the above problems in the prior art.
It is a primary object of the present invention to reduce substantially a time for fermentation of an organic waste material containing high percentage of water into a fertilizer, while permitting less space, less labor and less installation cost for fermentation by applying a single apparatus to both primary fermentation as aerobic fermentation and secondary fermentation as anaerobic fermentation.
Another object of the present invention is to offer a substantially improved allowable range of a percentage of water content in a treating object material, in addition to easy low-cost maintenance and management of an installation, without the need for a cutting work or the like having been required for primary fermentation and secondary fermentation.
A further object of the present invention is to permit a substantial reduction in time from the start of initial heating of a treating object material till the attainment of the peak temperature of fermentation, together with a stockyard saving and a prevention of offensive odor by deodorizing the treating object material through the process of attaining the peak temperature of fermentation to facilitate the following process of carrying back the fermented material to a farm and so on.
A method according to the present invention for achieving the above objects has the following features.
In a method of accommodating a treating object material consisting of an organic waste material containing a predetermined quantity of water in a fermentor for fermentation, the first feature of the method is that the treating object material is granulated in a nodular-shape before being accommodated in the fermentor for fermentation of the treating object material through mutually communicating ventilation spaces formed respectively between the surfaces of the adjacent granules of the treating object material.
The second feature is that the percentage of water content in the treating object material before being granulated is controlled until a percentage of water content enough to permit granulation and primary fermentation as aerobic fermentation is reached.
The third feature is that warm air is supplied to the treating object material accommodated in the fermentor until at least the treating object material is heated up to a temperature enough to keep up with primary fermentation as aerobic fermentation under an object temperature.
The fourth feature is that the treating object material having finished the primary fermentation is subjected to secondary fermentation as anaerobic fermentation in the same fermentor as that for the primary fermentation.
In a mechanism having a fermentation chamber for fermenting a treating object material consisting of an organic waste material accommodated in a fermentor and a warm air supply chamber provided at a lower part of the fermentation chamber through a ventilation floor ensuring well ventilation, the first feature of an apparatus according to the present invention is that a dispersing device for supplying warm air in a uniformly dispersed state toward the bottom of the fermentation chamber is provided on the inside of the warm air supply chamber.
The second feature of the apparatus is that the dispersing device is structured that a large number of pipes having well-ventilated outer walls are installed in or inserted into the air supply chamber in grating-shaped or panel-shaped combination, and warm air is supplied to the pipes.